The Capital Asset Pricing Model (CAPM) and the Single Index Model (SIM) are single factor models whose only risk factor is the market portfolio’s return. Say a Solar electricity generator company and a Beach bathing chair renting company are influenced by two factors, the market portfolio return and cloud cover in the sky. When it's sunny and not cloudy, both the Solar and Beach companies’ stock prices do well. When there’s dense cloud cover and no sun, both do poorly. Assume that cloud coverage risk is a systematic risk that cannot be diversified and that cloud cover has zero correlation with the market portfolio’s returns.

Which of the following statements about these two stocks is NOT correct?

The CAPM and SIM:

(a) Betas of the Solar and Beach companies will only measure the companies’ sensitivity to the market portfolio risk factor, not the cloud coverage factor.

(b) Will under-estimate the Solar and Beach stocks’ systematic variance.

(c) Will under-estimate the Solar and Beach stocks’ diversifiable variance.

(d) Models will show positive correlations between the Solar and Beach stock’s residual (also called idiosyncratic or diversifiable) returns.